Remote control of deflection in cathode-ray tubes



.BMOTE CONTROL '0F DEFLECTIQN IN CATHDE RAY TUB'ES v Filed Marchas',1944 I am artr- 5,

Patented .lune 24T, 1947 REMOTE CONTROL OF DEFLECTION IN CATHODE-RAYTUBES Madison G. Nicholson, Jr., Snyder, N. Y., assigner to ColonialRadio Corporation, Buffalo, N.

Application March 28, 1944, Serial No. 528,395

(Cl. Z50-11) 9 Claims.

This invention relates to a method and apparatus for remotelycontrolling the deflection in a cathode ray tube, particularly inrespect of angles or sectors to be observed; and while capable ofapplication for a number of purposes, is of particular utility and valuein connection with radar apparatus.

In such apparatus, it is known that signals may be transmitted from arotating antenna array rotating at a predetermined speed in such amanner that signals are sent out progressively in every direction. Ifthe waves which constitute these signals strike a conducting or metallicobject such as a ship, an airplane in night, or even tall buildings,they are reiiccted back, a, phenomenon sometimes termed radio echo.

One may employ a receivei to listen to this radio echo by observing iton an oscilloscope; and if the receiving antenna is located at the sameposition as the transmitter and has the same directional-characteristics and operates in synchronism with it, it is possible todetermine the bearing and the distance of the object which reilects thewave. In effect the observer looks around the entire horizon circle atthe same rate at which the transmitting antenna array rotates.

It is frequently desirable, however, instead of having one observercontinuously observing the entire 360 of the horizon, to observecontinuously a small sector; for example, to plot the course and speedof an airplane some miles away, and to follow this particular airplaneon its course.

In accordance with my invention, I provide a relatively simple andreliable means by which this may be done; that is, while thetransmitting antenna continues to rotate through 360 while sending outits signals, the receiver and cathode ray tube may be so controlled thatthe observer will look at only one part of the horizon; for example,that occurring within a compass bearing from 305, say, to 325, or thatwithin 310 to 320, depending on what is to be observed.

By the use of apparatus according to this invention, should the objectobserved move out of this area, it is possible by a simple adjustment ofthe apparatus to follow the object and to keep its indication centeredupon the screen of the cathode ray tube. Accordingly, among the objectsof my invention my be mentioned the following:

To provide simple and reliable apparatus for selecting any ydesiredsector of the horizon for continuous observation.

To provide simple apparatus by means of which the deection of thecathode ray may be controlled and maintained centered geographically inany particular sector.

'I'o provide means which may be remotely situated with respect to thecathode ray tube for executing such control.

Still other objects of my invention will be apparent from thespecification.

In this application I have particularly pointed out and distinctlyclaimed the part, improvement, or combination which I claim as myinvention or discovery, and I have explained the principles thereof andthe best mode in which I have contemplated applying those principles, soas to distinguish my invention from other inventions.

In the drawing,

Fig. 1 represents diagrammatically a radal system embodying myinvention.

Fig. 2 shows detailed views of the control apparatus and circuits inaccordance with this invention.

Fig. 3 is a diagrammatic View of a cathode. ray tube showing one mannerof connecting the same to the apparatus shown in Fig. 2.

Fig. 4 is a sketch indicating how the screen of the cathode ray tube mayappear with respect to the sector being observed.

Referring now more particularly to Fig. 1, II indicates generally thetransmitter of a locator system, which may comprise all of the necessaryapparatus, including the means for generating waves of the desiredfrequency, means for sending them out in pulses of the desired length,and a rotating antenna array driven by a motor Ill. The receiver,broadly indicated as I2, is usually connected to the transmitterantenna, which is used as the receiving antenna in the intervals betweentransmitted signals,

From the receiver connections may lead to the deflector amplifier I4 andto control grid ampliiier I5, feeding a suitable cathode ray tube Ildiagrammatically indicated in this instance as of the electrostatictype, in which case a relay I6 may be interposed between the controlgrid arnplier I5 and the cathode ray tube Il. In case a cathode ray tubeof the magnetic deection type is employed, relay I6 will not benecessary.

For the purpose of permitting the observer to continuously observe anyparticular sector of the horizon instead of having a panoramicview, Imay employ a position-controlling transmitter 20, and this willpreferably be associated with the transmitterA II and operated insynchronism with the' antenna array. This transmitter 2t may comprise arheostat 2| uniformly wound in the form of a ring.

so connected that their voltages are cumulative.`

The term opposite or opposite points, as used herein with reference torheostats 2i and 28, means two points so chosen and located on therheostat that the impedance between them is a maximum. If the impedanceof the rhe'ostat before it is closed on itself isX, then any twoopposite points will show an impedance between them equal to X/4, andmoving either peinty withA respect to the other will reduce theimpedance.

If the rheostats are woundy uniformly in ring form, as is preferable,then points at the end of any diameter will be opposite points inthesense deiined herein'.

The voltage between contacts 2'3 and 24 will always be the totalpotential difference of the source, and it will be apparent that halfway between points 23 and 24f on each sideof resistance 2 I there' willexist two pointsy between which .there is no difference of potential. Ifthe arm 22 is synchronized with the rotating transmitter atenna througha mechanicalconnection (not shown) in such' a manner that thedirectional pointer' 21 points' the direction in'- which the signals arebeamed, and this arm 21 is'v at right angles with the arm 22, then onerero point on resistance .2I will always rotate' in synchronism with,and have the same bearing asf, direction pointer 2l; that is, as arms 22and 2l rotate', being always at right angles to each other, the Zeropotential point will rotate synchronism with and 90 displaced frompoints 23 and 2d.

I may now provide at the receiver a second similar'l resistance '28, andcorresponding points of these two resistors may be interconnected as byconductors 30, 3|, 32, and .33, the lpoints of connection of conductor3l being labelled, for example, N for north, those of 33 E for east,those of 32 S for south, and those of 3 W for west. It will Vnow beobserved that the potential to ground from each of the points- N, E, S,-and VI, as the arm 22 rotates at a constant rate, is a sine wave, andthat each one of these is dise placed 90 fromv the next one. Rheostat 28may Je provided with two contact arms 40 and 4i, I'hese are preferablyso arranged that they have a, fixed angle of 90 between them, and arecon- ;inuously rotatable as a, unit.

Arm 40 may be connected to terminal A and yhence' to lateral deflectionplate 42 of the catlide ray tube Il, One of the vertical dellection)lates 45 may then be connected to the deiiecn ion' amplifier I4. Theremaining vertical delecting plate 44 may be connected to the otherateral deilec'ting plate 43, to the second anode E, and to ground. Thefirst anode 47 may be onnected to the focus control, or voltage source,s usual, and the control grid 49 may be con- ,ected to relay I6. Sincethis control grid usully has a very high potential diierence with re-'pect toground, of the order Vof 2,000 volts, and ich potentialdifference cannot be conveniently andled by the output of the controlgrid amplier I5, relay I6 is interposed responsive to op- :ation of theamplifier I so as to apply Va high negative or cutoff potential to thecontrol grid 49, as determined by amplifier I5.

The operation of the system may now be understood. Assume for the momentthat the transmitting antenna is stationary and is beamed northwest. Arm22 will be pointing northeast and southwest, the directional pointer Z'Iwill be pointing northwest, and these arms will remain stationary. Aspreviously pointed out, at a point half way between north and west therewill be z'ero voltage to ground, and the points N and W will be. equalin magnitude but of opposite polarity. Consequently points N and W onresistance 28 will be equal in magnitude but of opposite polarity, andata point half way between north and Vwest on resistance 28 there will bea point of zero potential with respect to ground.

With the setting of arm 40 as indicated; that is, at northwest, thepotential of point A and of lateral deflecting plate 42 will be zerowith respect to ground, and the cathode ray spot will be laterallycentered on the screen.

Suppose now that the transmitting antenna begins to rotate clockwise ata constant speed. It will be apparent that the potential of terminal Awill now describe a sine wave, the frequency of which is equal to thefrequency of rotation of the arm 22, and hence of the transmitting'antenna. This causes the cathode ray beam to deilect, for example, tothe right, reaching its maximum deflection at the time the antenna hasrotated through returning to the center at deecting to the leit to a.maximum at 270, and returning again to the center at 360 rotation.

From this it may be seen that, whatever the bearing of the arm 40, thescreen spot will be centered laterally when the transmitting antenna hasthe same bearing. It will be clear that if the maximum amplitude ofthedeecti'on of the cathode ray is less than that required to take it 01Tthe screen, the observer will see the entire' horizon, but if the sweepvoltages be adjusted to produce a maximum deflection which is muchgreater than the screen, then the observer will see only a part of thehorizon, and the greater the amplitude, the smaller 4the part he willsee To prevent the observer being confused hy an indication 180odirectionally off from where he wants to see, the voltage derived frompoint 4t may be applied through terminal B, the amplier I5, relay I6, tocontrol grid 4S. The effect of this is to apply a negative bias cuttingoff the ray during its return sweep from maximum deflection 'to theright to maximum deflection to the left.

Stated dilierently, during the sweep of the directional pointer fromsouthwest to northeast through northwest, the control grid will bebiased positively and the ray will be under the control of thedeflection plates. During the sweep of the directional pointer 21 fromnortheast to southwest through southeast, the second half of `its cycle,the control grid will be biased negatively and-the ray will be cut 01T.

Thus it will be seen that by setting the arm 40 to any bearing, theobserver may see a sector, the centerline of which has the same bearing,and the angular width of this .sector may be lncreased or decreased byadjusting the deilecting voltage to control the amount of deflection,the greater 'the deflection being, the smaller the angle observed. Thisis shown, ffor instance, in Fig. 4. Arm 40 is set to a bearing of315,.it'being desired to observe an .airplane which has Athat bearing'.The' sweep voltages may be adjusted so"v that the'angle observedis3052-325", but it will be'understood'-th`at', by increasing thesevoltages' still furthenth'e" angle may be reduced vto* trom 310 to 320.

' 1f' the airplane now travels so that its beariner gradually changesfrom 315 to 325, the peak indicated on the screen will displace itselftoward the righ-t, as indica-ted by the'dotted lines, and may eventuallyreachf the edge of the screen. Ii theobserver still-wishes tor follow.this plane, he will now resetthe arm di? to a bearing of 325-, whichwill move the' peak PA back tothe center of the screen. It will beunderstood that as many receiving elements 28 andrl cathode ray tubes ilmay be provided as it is desired to have observers and that eachobserver may be assigned to a specic object to follow in order tomaintain a continuous bearing on it, or each observer may be given aspecic angular portion of the horizon to watch continuously.

While I have shown and described certain preferred embodiments of myinvention, it will be understood that modifications and changes may bemade without departing from the spirit and scope of my invention, aswill be apparent to those skilled in the art.

I claim:

1. In a system for controlling the deflection in a cathode ray tube, inelement comprising an impedance closed upon itself, means for applying apotential difference to said impedance at opposite points, means forchanging the points of application of such potential difference whilemaintaining them at eleci trcally opposite points, a second impedanceclosed upon itself, a plurality of connections between like points onsaid impedances, a cathode ray tube, and means for deriving a potentialdiiference from said second impedance and applying it to control thedeflection of said cathode ray tube.

2. In a system for controlling the deection in a cathode ray tube, incombination, a transmitter element comprising an impedance closed uponitself, means for applying a potential difference to said impedance atopposite points, means for changing the points of application of suchpotential diierence while maintaining them at electrically oppositepoints, a second impedance closed upon itself, a plurality ofconnections between like points on said impedances, a cathode ray tube,means for deriving a potential diierence from said second impedance andapplying it to control the deection of said Cathode ray tube, and meansfor deriving a second potential diierence from said second impedance,for biasing the cathode ray on and off.

3. In a system for controlling the deflection in a cathode ray tube, incombination, a transmitter element comprising an impedance closed uponitself, means for applying a potential difference to said impedance atopposite points, means for cyclically changing the points of applicationof such potential difference while maintaining them at electricallyopposite points, a second impedance closed upon itself, a plurality ofconnections between like points on said impedances, a cathode ray tube,and means for deriving a potential difference from said second impedanceand applying it to control the deflection of said cathode ray tube.

Ll. In a system for controlling the deflection in a cathode ray tube, incombination, a transmitter element comprising an impedance closed uponcombination, a transmitter e.

itself, means for applying' a potential difference to said impedanceatopposite points, means for changing the pointsof application of suchpotential difference while maintainingV them vat electrically oppositepoints, a second impedance closed upon itself,v a plurality ofconnections between like points' on said impedances, a cathode rayytube, Vmeans for deriving a potential difference 'from' said secondimpedance and applying itto control the deflection of said cathode raytube, and means for deriving a second potential diiierence out of phasewith said'first potential difference from said second impedance, forbiasing the cathode ray on and oi.

5. Radio detection and ranging apparatus, comrising, in combination, atransmitter including a rotating antenna, a receiver synchronizedtherewith including a cathode ray tube, a direction indicatingtransmitting element synchronized with said antenna, having a continuousimpedance, rotary means synchronized with said antenna for applying apotential difference at opposite points on said impedance, a secondcontinuous impedance, a plurality of connections between symmetricalpoints on said impedances, a movable selecting connection to said secondimpedance, and connections from said selective connection to saidcathode ray tube to control the lateral deflection thereof.

6. Radio detection and ranging apparatus, comprising, in combination, atransmitter including a rotating antenna, a receiver synchronizedtherewith including a cathode ray tube, a direction indicatingtransmitting element synchronized with said antenna, having a continuousimpedance, rotary means synchronized with said antenna for applying apotential difference at opposite points on said impedance, a secondcontinuous impedance, a plurality of connections between symmetricalpoints on said impedances, a pair oi movable selective connections tosaid second impedance, said connections having a xed angularrelationship, connections from one of said movable connections to saidcathode ray tube to control the lateral deflection thereof, andconnections from the other of said movable connections to said cathoderay tube to bias the ray on and oi.

7. Radio detection and ranging apparatus, comprising, in combination, atransmitter including a rotating antenna, a receiver synchronizedtherewith including a cathode ray tube, a direction indicatingtransmitting element synohronized with said antenna,having a continuousimpedance, rotary means synchronized With said antenna for applying apotential difference at opposite points on said impedance, a secondcontinuous impedance, a plurality of connections between symmetricalpoints on said impedances, a pair of movable selective connections tosaid second impedance, said connections having a ixed angularrelationship, such as to provide quadrature phase relation between thevoltages from said connections, connections from one of said movableconnections to said cathode ray tube to control the lateral deflectionthereof, and connections from the other of said movable connections tosaid cathode ray tube to bias the ray on and oi.

8. The method of controlling the deflection in a cathode ray tube in aradio detection and ranging system transmitting signals successivelyaround the horizon and showing the radio echoes of such signals in acathode ray tube, which comprises applying a potential diiierence to aclosed path, moving the points of application of said potentialdiierence in synchronism With the bearing of transmitted signals,deriving a plurality of potential diiTerences from symmetrical points onsaid path, impressing said potential differences at corresponding pointsof a second and similar path, deriving a potential diierence betweenselected points of said second path, and applying said last potentialdiierence to control the lateral deflection of the cathode ray tube.

9. The method of controlling the deflection in a cathode ray tube in aradio detection and ranging system transmitting signals successivelyaround the horizon and showing the radio echoes of such signals in acathode ray tube, Which comprises applying a potential difference to aclosed path, moving the points of application of said potentialdifference in synchronism with the bearing of transmitted signals,deriving a plurality of potential differences from symmetrical points onsaid path, impressing said potential diierences at corresponding pointsof a second and similar path, deriving a pair of potential differenceshaving a predetermined and xed phase difference between selected pointsof said second path, applying one of said potential differences tocontrol the lateral deflection oi the cathode ray tube, and applying theother of said potential differences to bias the ray on and 01T.

MADISON G. NICHOLSON, JR.

